In recent years, RF communication systems have emerged as one of the major means of communicating data/messages from a first location to a second location. These days, the RF communication systems are being used in various fields such as, but not limited to, mobile communications system, Wi-Fi communication system, Bluetooth, and Wi-Max.
A typical RF communication system includes a data source, an encoder, a modulator, and an antenna. The data/messages to be transmitted originate from the data source. Thereafter, the encoder encodes the data/messages. The modulator modulates the encoded data/messages on an RF carrier signal. This RF carrier signal is then transmitted to the second location using the antenna. In certain scenarios, there may be a need to transmit the RF carrier signal to other components in the RF communication system (e.g., an RF power sensor) in addition to the transmission of the RF signal to the antenna. In such a case, an RF coupler is used to divide the power of the RF carrier signal into two (or more) portions such that the first portion of the power is supplied to the antenna and the second portion of the power is supplied to other components in the RF communication system.
FIG. 1 is a schematic diagram of a conventional RF coupler 100 in accordance with an embodiment. Conventional RF coupler 100 includes a first transmission line 102, a second transmission line 104, an input port 106, an output port 108, a coupled port 110, and an isolation port 112.
A first end and a second end, of first transmission line 102 are input port 106 and output port 108 respectively. A first end and a second end, of second transmission line 104 are coupled port 110 and isolation port 112 respectively. First transmission line 102 and second transmission line 104 are fabricated in close proximity of each other such that first transmission line 102 electromagnetically couples with second transmission line 104. Due to this, there exists a mutual inductance and a mutual capacitance between first transmission line 102 and second transmission line 104.
In operation, a first RF signal is applied to input port 106. Due to the mutual inductance and the mutual capacitance between first transmission line 102 and second transmission line 104, a portion of the first RF signal is induced in second transmission line 104 (hereinafter referred as the second RF signal). The second RF signal traverses through second transmission line 104. Further, the second RF signal is obtained from coupled port 110. The remaining portion of the first RF signal traverses through first transmission line 102 and is obtained from output port 108.
Conventional RF coupler 100 incurs losses due to the induction of the second RF signal in second transmission line 104. Examples of such losses include insertion losses (i.e., ratio of power of the RF signal at output port 108 to power of the RF signal at input port 106), coupling losses (i.e., ratio of power of the RF signal at coupled port 110 to power of the RF signal at input port 106), dielectric losses, conductor losses, etc. Accordingly, there is a need for an invention that reduces such losses in RF couplers.